Continuous ZIF-8 membranes effectively separated air/Xe gas mixtures. These membranes showed air permeances as high as 3.94 × 10-8 mol m-2 s-1 Pa-1 and separation selectivities as high as 12.4 for an air/Xe molar feed composition of 9 : 1. These membranes separated air from Xe via molecular sieving, preferential adsorption, and diffusivity differences.